An abundant - though little-known - natural remedy for gram-positive bacterial infections is botanically called Usnea (pronounced ooze-knee-ah), or commonly called old-man's beard. It's a gray lichen typically growing in tufts on tree branches. Usnea species grow all around the world, with several species being native to North America.

Usnea lichen is a symbiote, or two plants living symbiotically. One way to identify Usnea is to gently pull apart a strand, exposing the inner plant, resembling a thin, white thread, while the greyish-green covering is the outer plant.

Staph and Enterococci strains have developed the ability to share antibiotic-resistant genes, creating what's been dubbed "superbugs" because they have developed methods to resist the most powerful pharmaceutical antibiotics. Superbug strains commonly appear in nursing homes, hospitals and prisons where the population generally has a lowered immunity and is in confined quarters.

Usnea, as well as other plants with antibacterial properties, contains a complexity of chemical compounds. While the most prominent antibacterial compound in all Usnea species is usnic acid, other unidentified compounds, or compounds with unknown attributes, seem to enhance Usnea's antibacterial qualities, including out-smarting bacterial adaptation to antibiotics.

Traditional and historical medicinal uses of Usnea have been for external skin infections, boils, wounds and internal respiratory infections.

During the medieval period, Usnea lichen, which is derived from the Arabic name for moss, u na, also was called "moss from a dead man's skull." Usnea found growing on unburied skulls was considered the most medicinally potent form, especially when the skull was from a person who was executed. It was thought that the corpse's vital force lingered longer if one had died suddenly, than if someone died from natural causes. A common use for Usnea in medieval Europe was in wound salve compounds. If effective, this likely was due to the lichen's antibacterial qualities, according to P. Modenesi, botanical researcher at Universit di Genova, Italy.

Current scientific research has found Usnea to be antioxidant and hepatoprotective; however, toxicologists are studying Usnea species for being toxic to the liver. Usnea can accumulate heavy metals, serving as a biomarker of air quality. Cases of liver toxicity might be due to Usnea harvested in toxic locations, rather than caused by Usnea itself. Take care in gathering Usnea away from industrial sites, railways and roadways.

Although Usnea usually grows in tree branches, harvesting it is easy after a strong windstorm, when branches have been blown to the ground. Large amounts of Usnea can be harvested in such cases rather quickly.

To prepare Usnea as medicine, the herb must be ground to expose as much cell surface as possible, and used in powder form or extracted in a mixed alcohol-water solution such as a tea or tincture.

• Holli Richey has a master's degree in herbal medicine and lives in Athens. For more information, visit her blog at hollirichey.com, or e-mail her at herichey@gmail.com.